For example, a technique shown in Japanese Patent Application Publication No. S59-25437 is conventionally known as a technique for avoiding inquiry concentration in the communication between automobiles (so-called communication between vehicles). In this technique, while an inquiry automobile dynamically establishes a transmission path through another relay automobile, a vehicle possessing response information of a predetermined desirable area is retrieved. The retrieved response information possessing vehicle sends-out the response information to the transmission path previously established so that the response information is transmitted to the inquiry automobile. In this case, all the relay automobiles and inquiry automobile possess the sent-out response information. With respect to the subsequent same inquiry, each of the relay automobiles and the inquiry automobile sends out the response information so that the inquiry concentration can be avoided.
Each automobile is managed by a wireless base station in every area. When the automobile is advanced into a jurisdiction area, the wireless base station gives an identification number to its automobile. When the automobile having the given identification number is retired from the jurisdiction area, the given identification number is deprived and information collected during a movement of this automobile within the jurisdiction area is collected from this automobile and is held. The communication device is constructed so as to retrieve and acquire information mutually held in the wireless base stations.
Therefore, even when no inquiry automobile can retrieve the response information possessing vehicle (no transmission path can be established), the information of a predetermined desirable area can be acquired by making an inquiry to the wireless base station of the existing area of the inquiry automobile.
In the technique described in Japanese Patent Application Publication No. S59-25437, the relay automobile is selected by an angle formed by an advancing direction of the inquiry automobile and the direction of a destination area (an area desirous to acquire information), an angle formed by the advancing direction of the relay automobile and the direction of the destination area, etc. so as to efficiently establish the transmission path. Such angles are momentarily changed as the automobile is moved. Moreover, such angles are greatly changed in accordance with the shape of a road and right and left turnings of the vehicle. Therefore, high speed calculation capability is required in the communication device of each automobile.
Further, information relating to the direction of the destination area is adapted so as to be acquired from the wireless base station. Therefore, it is indispensable that the communication device can communicate with the wireless base station. When the automobile passes through a place unable to communicate with the wireless base station as in the interior of a tunnel, a problem exists in that no relay automobile can be selected and no transmission path can be established.